Cocoa shells (also known as cocoa hulls and cocoa husks) are the outer portions of cocoa beans which encase the inner nibs of the beans. The shell of a cocoa bean constitutes approximately 12-15% of the total mass of the bean.
Cocoa nibs and shells are typically separated by cracking cocoa beans and removing the shells. Cocoa beans may be cracked using, for example, mechanical rollers and/or heat treatment (e.g. infrared heat treatment) and the shells and nibs separated by a process known as “winnowing”, which operates on the basis of the different densities of the shells and nibs. Separation of cocoa shells and nibs may be performed after cocoa beans have been fermented to aid in the development of certain flavours. Cocoa beans may also be roasted prior to separation of the shells and nibs to develop the taste and aroma of the beans and to assist in loosening the shells.
Following separation from cocoa shells, cocoa nibs are typically processed by reducing the fat content of the nibs and grinding the nibs to produce cocoa powder for use in various foods such as chocolate and cocoa beverages. The following illustrates a typical process for producing cocoa powder:
Cocoa nibs are first ground, usually in two stages (e.g. beater-blade milling followed by ball milling) to produce a liquor. The liquor is heated to a temperature typically greater than 110° C. and subsequently pressed under high pressure (e.g. 540 bar) to remove a portion of the cocoa butter from the liquor. The resulting cocoa cake has to be pre-broken, and is then typically fine milled in two steps using, for example, 2-pin mills (the pines of which are different sizes) produce cocoa powder. Such processing of cocoa nibs is expensive in terms of the energy and equipment required to produce a fine cocoa powder having acceptable organoleptic properties.
A further disadvantage of cocoa powder produced from fat-reduced and ground cocoa nibs (hereinafter “cocoa powder”) is that it induces a bitter aftertaste in foods. Moreover, cocoa powder still has a high fat content relative to its calorific content. The need to at least partially remove the fatty cocoa butter component of cocoa nibs, which constitutes about 50-55 mass % of the nibs, contributes to the expense of producing cocoa powder.
Cocoa shells are generally viewed as an unwanted by-product of cocoa powder manufacture. Indeed, the 1973 EU Chocolate Directive limits the amount of cocoa shells in cocoa products to not more than 2% based on the total mass of the product.
As a consequence, cocoa shells are usually discarded or utilized in fertilizers or animal feed following separation from cocoa nibs. For example, U.S. Pat. No. 4,070,487 discloses the use of cocoa shells in ruminant feed in order to increase the appetite of ruminants such as lambs and calves.
The use of cocoa shell extracts is also known. For example, U.S. Pat. No. 4,156,030 discloses a method in which cocoa shells are extracted using an acidified ethanol solution. The extract is separated from the cocoa shell residue, for example, using a filter press, and the extract is used to produce a water-soluble berry-like flavouring and colouring material for foods. The cocoa shell residue is discarded, preferably following recovery of ethanol from the residue.
U.S. Pat. No. 4,532,147 also relates to extracts of cocoa shells. Specifically, waste cocoa material such as a cocoa shell-containing material is treated with an aqueous alcoholic medium to extract pigments from the material. The liquid phase is subsequently separated from the cocoa material and the aqueous medium removed to yield a flavourless and coloured extract.
Cocoa shell extracts as disclosed in the above-mentioned documents are not capable of providing foods to which they are added with an acceptable chocolate flavour. The extracts are also unsuitable as a useful source of nutrients such as insoluble dietary fibre, and the extracts are not suited to improving the texture (e.g. spreadability) of a food. Moreover, extraction of cocoa shells is costly, particularly since it requires considerable amounts of solvents.
In terms of the use of cocoa shells per se, EP 1 733 624 A1 indicates that cocoa shells may be incorporated into foods such as chocolate and cocoa beverages.